Alarm attachment for doorknobs



U ITED TES PATENT OFFICE HARRY nxmztou, or sou'rn TACOMA, WASHINGTON- ALARM nrrnonmnnrronjnoonxnons.

To all whom it magfconcm:

Be it known that I, HARRY R. Knrron, a citizen of the United States, residing at South Tacoma, in the county of Pierce and State of Washington, have invented certain new and useful Improvements in Alarm Attachments for Doorknobs, of which the following is a specification.

The present invention relates to alarm attachments for door knobs,.the primary object of which is to provide a very simple mechanism which may be quickly attached to a door and connected to a doorknob for giving an audible signal as soon as the knob is turned, the signal being effective until the knob is permitted to return to its normal position. i

The above and other objects of this invention will be in part described and in part understood from the following description of. the present preferred embodiment of the invention taken in connection with the aocompanying drawings, wherein:

Fig. 1, is afront elevational view of an alarm mechanism constructed in accordance with this invention illustrating its application.

Fig. 2, is a side elevational view thereof, and

Fig. 3, is a rear elevational' vie-w of the device.

In order to illustrate the application of this invention a portion of a door at is shown which has associated therewith a door knob spindle 5 of the usual or any desired form.

The device of this invention consists especially of a bell 6 which has associated therewith an alarm mechanism housed in a casing 7 The alarm mechanism may be of standard design which will continuously ring the bell 6 until mechanical means are used to stop the same. The mechanism is set by a lever 8, which extends through a slot in the periphery of the casing 7. An abutment pin 9 extends rearwardly from the casing 7 said pin being carried by the alarm mechanism. The spring may be wound by a key 10, which extends through the hell 6.

A plate generally designated 11 is provided, the upper end 12 of which is of a circular configuration for engagement over the casing 7 to capacitate as a guard plate and is provided with an opening through which the pin 9 extends. The lower end of the plate issues into a guide member 13 which is formed by bending the lateral. ma gins 14c Specification of Letters Patent. Patented Jan. 3, Application fiIedEebYuary jSerialNoi i lfia l. g i A thereof downwardly and outwardly for engagement with the door 4:. These margins are secured to the door preferably as shown in Fig. 1 of the drawings.

Theguard plate 12 has pivotally mounted thereon a bell crank'lever 15, the axis of which is preferably arranged below and substantially in vertical alignment with the pin 9. One angle of the bell crank is adapted for engagement with the pin 9, while the opposite. angle is in pivotal engagement with one end of a rocking lever .16. The opposite end of said lever pivotally connects with a portion 17 which is extended from the door knob spindle engaging member 18. This member consists of a pair of straps which are bent to conform to the shape of the spindle and are connected together directly above and below the latter by means of bolts 19. v

In use of this device the plate 11 is secured to the door above the door knob spindle 5 in a manner shown in Fig. 1. In this position it will be noted that the lever 16 extends downwardly beneath the guide 13 pin 9 when thedoor knob is in a normal position, thereby retaining the clapper of the alarm" mechanism in a fixed position. The lever 8 may be set so as to permit the alarm mechanism to operate, or to render it inoperative at the option of the user. Assuming, however, that this leve'r has been set to permit movement of the clapper for ringing the bell, just as soon as the door knob spindle has been turned, motion is imparted to the lever 16 to operate the bell crank lever, thereby disengaging the same from the pin 9 and causing the bell to ring.

As soon as the knob is permitted to turn to its normal position, the bell crank lever will automatically return into engagement with the pin 9, thereby preventing further movement of the clapper and correspondingly preventing ringingof the bell. It is the intention that the alarm mechanism will be rendered inoperative during the day by the lever 8 and at night when the door is being locked the lever 8 will be set so as to cause the alarm to ring as soon as the door knob has been turned.

It is to be understood that various changes may be made in this device especially in the details of construction, proportion and arrangement of parts without departing from the spirit and scope of the invention as covered by the appended claim.

What is claimed is:

An alarm for door knobs including an incased alarm mechanism ofi'set from the door a plate one end of which conforms to the shape of the alarm mechanism casing and is engaged therewith, the lateral ,margins of the plate being pressed inwardly, to lie'in a plane parallel with the body of the'plate, and secured to the door, and means connectdsaid mechanism and door knob and slidable between the inwardly pressed margins 'of saidplate "whereby movement 15 RUoK C. MGGA E, 1 HAsK N. 

